为什么新的InputStreamReader不会读取控制台中的其余字符？ [英] Why a new InputStreamReader won't read the remaining characters in the console?

问题描述

所以我有一个用Java编写的非常简单的服务器：

So I have a very simple server written in Java:

public class SimpleServer {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("Server Socket created, waiting for client...");
        Socket accept = serverSocket.accept();
        InputStreamReader inputStreamReader = new InputStreamReader(accept.getInputStream());
        int read;
        System.out.println("Client connected, waiting for input");
        while ((read = inputStreamReader.read()) != -1) {
            System.out.print((char) read);
        }
    }
}

这是一个代码我用来连接它：

And here is a code that I use to connect to it:

public class SimpleClient {

    public static void main(String[] args) throws Exception {

        Socket socket = new Socket("localhost",8888);
        OutputStreamWriter outputStream = new OutputStreamWriter(socket.getOutputStream());

        InputStreamReader inputStreamReader;
        char[] chars = new char[5];

        while (true) {
            System.out.println("Say something: ");
            inputStreamReader = new InputStreamReader(System.in);
            inputStreamReader.read(chars);
            int x = 0;
            for (int i=0;i<5;i++) {
                if(chars[i]!='\u0000') {
                    x++;
                }
            }
            outputStream.write(chars,0,x);
            outputStream.flush();
            chars = new char[5];
        }

    }

}

现在，当我在客户终端输入类似的内容时：

Now when I type something like this in the terminal of the Client:

123456789

我将在服务器的终端中看到：

I will see in the terminal of the Server:

Server Socket created, waiting for client...
Client connected, waiting for input
12345

但是，当我按如下方式更改客户时：

However, when I change client as follows:

public class SimpleClient {

    public static void main(String[] args) throws Exception {

        Socket socket = new Socket("localhost",8888);
        OutputStreamWriter outputStream = new OutputStreamWriter(socket.getOutputStream());

        InputStreamReader inputStreamReader = new InputStreamReader(System.in);
        char[] chars = new char[5];

        while (true) {
            System.out.println("Say something: ");
            inputStreamReader.read(chars);
            int x = 0;
            for (int i=0;i<5;i++) {
                if(chars[i]!='\u0000') {
                    x++;
                }
            }
            outputStream.write(chars,0,x);
            outputStream.flush();
            chars = new char[5];
        }

    }

}

然后对于相同的输入，我将看到：

then for the same input, I will see:

Server Socket created, waiting for client...
Client connected, waiting for input
123456789

我的问题是， System.out 是一个静态变量，在这种情况下已经打开并连接到终端。为什么创建新的InputStreamReader对象时终端中的信息会丢失？相同的终端传递给对象，不是吗？

My question is, System.out is a static variable which is already open and connected to the terminal in this case. Why is the information in the terminal lost when a new InputStreamReader object is created? Same terminal is passed to the object, isn't it?

推荐答案

为什么在创建新的InputStreamReader对象时终端中的信息会丢失？

Why is the information in the terminal lost when a new InputStreamReader object is created?

当您在 InputStreamReader <上调用 read（）时/ code>，它允许（并且经常会）从流中读取比实际请求更多的数据，并将其余数据存储在缓冲区中，以满足以后的读取来电。我怀疑整个文本行实际上是由第一个 InputStreamReader 读取的，所以当你构造第二个 时对于同一个流，InputStreamReader 没有任何内容可供阅读，你必须输入更多文本才能让它做任何事情。

When you call read() on the InputStreamReader, it's allowed to (and often will) read more data from the stream than you've actually requested, and store the rest in a buffer, to satisfy later read calls. I suspect the whole of the line of text has actually been read by the first InputStreamReader, so when you construct a second InputStreamReader for the same stream, there's nothing left for it to read, and you'd have to type in more text to get it to do anything.

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